Design Patterns in Java TutorialDesign patterns represent the best practices used by experienced object-oriented software developers. Design patterns are solutions to general problems that software developers faced during software development. These solutions were obtained by trial and error by numerous software developers over quite a substantial period of time. This tutorial will take you through step by step approach and examples using Java while learning Design Pattern concepts.

AudienceThis reference has been prepared for the experienced developers to provide best solutions to certain problems faced during software development and for un-experienced developers to learn software design in an easy and faster way.

PrerequisitesBefore proceeding with this tutorial you should have a good understanding of Java programming language. A basic understanding of Eclipse IDE is also required because all the examples have been compiled using Eclipse IDE.

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Software designpattern
In software engineering, a designpattern is a general reusable solution to a commonly occurring problem within a given context in software design. A designpattern is not a finished design that can be transformed directly into source or machine code. It is a description or template for how to solve a problem that can be used in many different situations. Patterns are formalized best practices that the programmer must implement themselves in the application.[1] Object-oriented designpatterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Many patterns imply object-orientation or more generally mutable state, and so may not be as applicable in functional programming languages, in which data is immutable or treated as such.
Designpatterns reside in the domain of modules and interconnections. At a higher level there are architectural patterns that are larger in scope, usually describing an overall pattern followed by an entire system.[2]
There are many types of designpatterns, for instance
* Algorithm strategy...

...generally two schools of thought on how to proceed. You could plan and develop a solution completely from scratch, relying on your project team’s understanding and innovative design abilities to solve all issues that arise from your development effort. Alternatively, you could make use of a designpattern that gives you a templateto follow towards designing a complete solution that solves different issues for different situations as they arise. That is the idea behind designpatterns. They are not complete solutions themselves that can be magically turned into code. But, they can be used as templates for solving development problems by using the fundamentals behind object-oriented design which define and use the relationships between classes and objects themselves, keeping them general enough to be reused over and over. As you can imagine, because they are generic, there are plenty of designpatterns that exist. They range from the simple to the complex and each has its own pros and cons when deciding which to use in your development project. What follows is a compare and contrast of a sampling of the variety of designpatterns in existence.
Adapter DesignPattern
The first designpattern we will explore is the Adapter pattern, also known as the wrapper...

...DesignPattern Matrix
DesignPatterns: From Analysis to Implementation by
This is an excerpt from the manuals for DesignPatterns Explained: A New Perspective for Object-Oriented Design Not all of the Gang of Four designpatterns are included because not all of them are covered in the course. Furthermore, we use a variation on the classification of the GoF patterns:
The Decorator and Proxy patterns are classified as Structural patterns by the GoF. Since they both add instead of just combining functionality, I believe they are more behavioral in nature. In our minds, the Bridge can be considered as either a Structural or Behavioral pattern. As a structural pattern, it allows the use of two different, given, implementation in the same way. As a behaviorally pattern, it helps identify that there are variations of an implementation. We have also reclassified several Behavioral patterns as Decoupling patterns (a new classification of ours). That is because these patterns are more about decoupling than about managing new behavior.
This is a work in progress. Updates will be announced through our e-zine. You can subscribe to this by sending a message to info@netobjectives.com and putting subscribe in the subject. Contents:...

...DesignPatternsDesignPatterns
Elements of Reusable Object
Oriented Software
Pag 1 de
358
Gamma – Helm - Johnson – Vlissides
Preface
This book isn't an introduction to object-oriented technology or design. Many books already do a good job of
that. This book assumes you are reasonably proficient in at least one object-oriented programming language,
and you should have some experience in object-oriented design as well. You definitely shouldn't have to rush to
the nearest dictionary the moment we mention "types" and "polymorphism," or "interface" as opposed to
"implementation" inheritance.
On the other hand, this isn't an advanced technical treatise either. It's a book of designpatterns that describes
simple and elegant solutions to specific problems in object-oriented software design. Designpatterns capture
solutions that have developed and evolved over time. Hence they aren't the designs people tend to generate
initially. They reflect untold redesign and recoding as developers have struggled for greater reuse and flexibility
in their software. Designpatterns capture these solutions in a succinct and easily applied form.
The designpatterns require neither unusual language features nor amazing programming tricks with which...

...and externalize an object's internal state so that the object can be restored to this state later.
The memento pattern is a software designpattern that provides the ability to restore an object to its previous state (undo via rollback).
The memento pattern is used by two objects: the originator and a caretaker. The originator is some object that has an internal state. The caretaker is going to do something to the originator, but wants to be able to undo the change. The caretaker first asks the originator for a memento object. Then it does whatever operation (or sequence of operations) it was going to do. To roll back to the state before the operations, it returns the memento object to the originator. The memento object itself is an opaque object (one which the caretaker cannot, or should not, change). When using this pattern, care should be taken if the originator may change other objects or resources - the memento pattern operates on a single object.
2. CHAIN OF RESPONSIBILITY
[pic]
Type: Behavioral
What it is: avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.
In Object Oriented Design, the chain-of-responsibility pattern is a...

...2014
BSIT-3A Prof. Nueva
“Good Design results in Good programs”
There’s a lot of program nowadays that are emerging because of many reasons. The number one reason is that it is easy to use. Another is that it is said to be efficient and lastly is that it is eye-catching. Eye-catching, in the sense that it easily attracts users not only because of its beauty but also they assure the effectiveness and productivity of the program that they will use.
A program now should be tested in order to qualify to the needs of the users. In order to meet these needs, a program should use a step-by-step procedure for it to be executable. This step includes the engineering phase, the design phase, the implementation (which is the actual programming), testing and lastly the maintenance (which is responsible in maintaining the user’s satisfaction). Out of all this phases, the design will be the one that I will be focusing on. But before that let’s look back to what we have understood in this phase.
During the design phase, a model of the whole system is developed that when it is coded in some programming language, solves the problem of the user. The problem is then dissolved into manageable pieces called modules or components. The purpose of these modules and the interfaces between them are specified in a very precise way.
This is why the Design is one of the most important parts in producing a good...